Plumb line



FIG. 1 is a top plan view of a plumb line showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is an elevational view taken from the right-hand side of FIG. 2;

FIG. 5 is an elevational view taken from the left-hand side of FIG. 2;

FIG. 6 is a top perspective view of the plumb line of FIG. 1.; and,

FIG. 7 is a bottom perspective view of the plumb line of FIG. 1. 

The ornamental design for a plumb line, as shown and described. 